Motor Actuator and Opening/Closing Device

ABSTRACT

In a driving force transmission mechanism in a motor type damper device, when a small AC synchronous motor rotates in one direction and a tooth-missing gear part of a tooth-missing gear engages with the first rack part of a rack member the rack member is moved upward to operate a baffle in an open direction and, when the tooth-missing gear part engages with the second rack part of the rack member, the rack member is moved downward to operate the baffle in a close direction. In this manner, even when the baffle and the rack member are operated in both directions, the tooth-missing gear is required to be rotated in only one direction and the rotation of the small AC synchronous motor is not required to be reversed. Therefore, the structure of a control circuit for the motor type damper device can be simplified.

This is a U.S. national stage of application No. PCT/JP2006/300376,filed on 13 Jan. 2006. Priority under 35 U.S.C. §119(a) and 35 U.S.C.§365(b) is claimed from Japanese Application No. JP 2005-8286, filed 14Jan. 2005, the disclosure of which is also incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to a motor actuator with which a drivingforce of a motor is transmitted to a driven member through a drivingforce transmission mechanism for operating the driven member and relatesto an opening/closing device for operating an opening/closing memberwhich is used in a refrigerator or the like.

BACKGROUND ART

Conventionally, for example, a motor type damper device for controllingthe taking of cold air in a refrigerator has been known as a motor unit(motor actuator) in which a motor such as an AC synchronous motor or astepping motor is used as a drive source (see, for example, JapanesePatent Laid-Open No. Hei 6-109354).

In the case of the motor type damper device which is disclosed in theabove-mentioned Japanese Patent Laid-Open No. Hei 6-109354, a baffle anda drive mechanism part such as a motor are disposed across a rotaryfulcrum shaft. When the motor is rotated in one direction to move a rackupward, an engaging shaft abuts with an upper face of a hollow portionto turn the baffle in an open direction and thus an intake opening forcold air is opened. Further, when the motor is rotated in the otherdirection, a lower portion of the engaging shaft abuts with the elasticpiece of an elastic plate and depresses it downward to turn the bafflein a close direction.

DISCLOSURE OF THE INVENTION

However, in the case of the damper device described in Japanese PatentLaid-Open No. Hei 6-109354, opening/closing of the baffle is performedby means of that the motor is forwardly and reversely rotated to movethe engaging shaft up and down and thus the structure of a controlcircuit for changing the rotating direction of the motor becomescomplicated.

In view of the problems described above, the present invention mayprovide a motor actuator in which the rotation of a motor is notrequired to be reversed even when a driven member is operated in bothdirections. Further, another object of the present invention is toprovide an opening/closing device in which the rotation of a motor isnot required to be reversed when an opening/closing member is performedin an opening and a closing operations.

Thus, there may be provided a motor actuator in which a driving force bya motor is transmitted to a driven member through a driving forcetransmission mechanism to operate the driven member, characterized inthat, the driving force transmission mechanism comprises a gear which isrotationally driven by the motor and a rack member which is linearlydriven by the gear to operate the driven member, and the gear isprovided with a tooth-missing gear part in which a teeth part is formedat a predetermined position in a circumferential direction of the gear,and the rack member is provided with a first rack part which causes therack member to move in one direction when the motor rotates in onedirection and the first rack part engages with the tooth-missing gearpart and a second rack part which causes the rack member to move in theother direction when the motor rotates in the above-mentioned onedirection and the second rack part engages with the tooth-missing gearpart.

In a motor actuator, when the motor in the driving force transmissionmechanism rotates in one direction and the tooth-missing gear partengages with the first rack part of the rack member, the rack member maybe moved in one direction to operate the driven member in apredetermined direction, and when the tooth-missing gear part engageswith the second rack part of the rack member, the rack member is movedin the other direction to operate the driven member in an oppositedirection. As described above, even when the driven member is operatedin both directions, the gear is required to be turned in only onedirection and the rotation of the motor is not required to be reversedand thus the structure of a control circuit of the motor actuator can besimplified.

Thus, it is preferable that the tooth-missing gear part is in anon-engagement state with the second rack part when the tooth-missinggear part engages with the first rack part, and the tooth-missing gearpart is in a non-engagement state with the first rack part when thetooth-missing gear part engages with the second rack part. According tothe structure as described above, when the tooth-missing gear partengages with the first rack part to move the rack member in onedirection, since the tooth-missing gear part does not engage with thesecond rack part, the rack member does not receive unnecessary forcebetween the second rack part and the tooth-missing gear part. On theother hand, when the tooth-missing gear part engages with the secondrack part to move the rack member in the other direction, since thetooth-missing gear part does not engage with the first rack part, therack member does not receive unnecessary force between the first rackpart and the tooth-missing gear part.

Thus, it is preferable that the first rack part and the second rack partare extended in parallel to each other. According to the structure asdescribed above, the rack member can be reciprocated only in thedirection where the first rack part and the second rack part areextended and thus operating space of the rack member can be narrowed.Accordingly, the size of the motor actuator can be reduced.

Thus, it is also preferable that the rack member is provided with a pairof inner side portions between which the gear is disposed and which areextended in parallel to each other, and the first rack part is formed inone of a pair of the inner side portions and the second rack part isformed in the other of a pair of the inner side portions. According tothe structure as described above, the rack member can be driven in bothdirections with only one gear and thus the number of components andspace can be reduced. Further, since the first rack part and the secondrack part are extended in parallel to each other, the rack member can bereciprocated only in the direction in which the first rack part and thesecond rack part are extended. Therefore, since operating space of therack member may be narrowed, the size of the motor actuator can bereduced.

Thus, it may be structured that the driving force transmission mechanismincludes, as the gear, a first gear on one side of both side positionsof the rack member and a second gear on the other side of the both sidepositions, and the rack member is provided with a pair of outer sideportions which respectively face on opposite sides and are extended inparallel to each other, and the first rack part is formed in one of apair of the outer side portions and the second rack part is formed inthe other of a pair of the outer side portions. According to thestructure as described above, since the rack member can be reciprocatedonly in the direction in which the first rack part and the second rackpart are extended, operating space of the rack member may be narrowed.Therefore, the size of the motor actuator can be reduced.

The motor actuator to which the present invention is applied can beused, for example, in an opening/closing device. In this case, thedriven member is an opening/closing member whose position is changed toan open position or a close position by the rack member.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, withreference to the accompanying drawings which are meant to be exemplary,not limiting, and wherein like elements are numbered alike in severalFigures, in which:

FIG. 1 (A) is a partly sectional view showing an opening/closing deviceand (B) is a rear view showing the opening/closing device which isviewed from the direction of “a”.

FIG. 2 (A) is a plan view showing a geared motor which is used in theopening/closing device shown in FIG. 1 and (B) is a developed viewshowing a gear train of the geared motor.

FIG. 3 (A), (B), (C), (D) and (E) are explanatory views showingoperations of the opening/closing device shown in FIG. 1.

FIG. 4 a block diagram showing a control circuit of a refrigerator onwhich the opening/closing device shown in FIG. 1 is mounted.

FIG. 5 a timing chart showing operations of a baffle and switches in theopening/closing device shown in FIG. 1.

FIG. 6 an explanatory view showing another opening/closing device towhich the present invention is applied.

FIG. 7 a plan view showing another opening/closing device.

EXPLANATION OF REFERENCE NUMERALS

-   -   1 motor type damper device (opening/closing device)    -   2 small AC synchronous motor    -   3 driving force transmission mechanism    -   7 baffle    -   8 rack member    -   46 tooth-missing gear (gear)    -   461 gear part    -   462 tooth-missing gear part    -   463 teeth part    -   47 first rack part    -   48 second rack part    -   49 connecting part

BEST MODE FOR CARRYING OUT THE INVENTION

As a motor actuator to which the present invention is applied, anopening/closing device for causing a baffle (driven member) used in arefrigerator to perform opening or closing operation will be describedbelow with reference to the accompanying drawings.

(Entire Structure of Opening/Closing Device)

FIG. 1(A) is a partly sectional explanatory view showing anopening/closing device to which the present invention is applied andFIG. 1(B) is a rear view showing the opening/closing device which isviewed from the direction of “a” in FIG. 1(A). FIG. 2(A) is a plan viewshowing a geared motor which is used in the opening/closing device shownin FIG. 1 and FIG. 2(B) is a developed view showing a gear train of thegeared motor. FIGS. 3(A), 3(B), 3(C), 3(D) and 3(E) are explanatoryviews for explaining the structure and operation of the opening/closingdevice shown in FIG. 1. The left side views show positionalrelationships between a cam member and contact pieces which are viewedfrom the same direction as FIG. 2(A) and the right side views showpositional relationships between a rack member and a tooth-missing gearwhich are viewed from the same direction as FIG. 2(A).

The opening/closing device shown in FIGS. 1(A) and 1(B) and FIGS. 2(A)and 2(B) is a kind of motor unit. Specifically, the opening/closingdevice is a motor type damper device 1 for cutting off cold air that isdriven by a small AC synchronous motor in a refrigerator.

The motor type damper device 1 includes a small AC synchronous motor 2as a motor and a driving force transmission mechanism 3 for transmittinga driving force of the small AC synchronous motor 2. A geared motor(motor actuator) is structured with the small AC synchronous motor 2 andthe driving force transmission mechanism 3.

As shown in FIGS. 1(A) and 1(B), the motor type damper device 1 includesa pipe-shaped frame 4 whose both ends are opened, an opening part 5which is formed in the inside of the frame 4, and a baffle 7 as anopening/closing member (driven member) which turns about a fulcrum shaft6 to perform opening and closing operation of the opening part 5. Theopening part 5 is opened or closed by using the baffle 7 to controlsupply of cold air to a chamber. In a connecting portion which is formedon an underside of the baffle 7 in the motor type damper device 1, ahollow part 71 is formed at an eccentric position to the fulcrum shaft6. A protruded part 86 which is protruded in a side direction at the tipend of an output part 85 of a rack member 8 of the driving forcetransmission mechanism 3 is inserted into the hollow part 71. A sheet 90comprised of polyethylene foam which is an elastic body is provided onthe rear face of the baffle 7 which is located on the side of theopening part 5 to fully close the opening part 5 when the baffle 7 isclosed.

As shown in FIGS. 2(A) and 2(B), the driving force transmissionmechanism 3 includes a gear train part II mechanically connected to thesmall AC synchronous motor 2, a cam part 465 formed in a gear(tooth-missing gear 46 which is a gear having a tooth-missing gear) ofthe last stage of the gear train part 11 and the rack member 8. Thedriving force transmission mechanism 3 is disposed in the inside of acase body 15. The case body 15 is structured by means of that a lowercase 13 and an upper case 14 are fixed to each other with screws. Thesmall AC synchronous motor 2 is commonly used and thus its detaildescription is omitted.

The gear train part 11 includes a first gear 42 which engages with apinion 32 fixed to an output shaft of the small AC synchronous motor 2,a second gear 43 which engages with a pinion portion of the first gear42, a third gear 44 which engages with a pinion portion of the secondgear 43, a fourth gear 45 which engages with a pinion portion of thethird gear 44, and a tooth-missing gear 46 (gear) as a fifth gear whichis provided with a gear part 461 engaging with the fourth gear 45. Thegear part 461 of the tooth-missing gear 46 is formed with teeth aroundthe entire circumference.

As shown in FIGS. 2(A), 2(B) and 3(A), the rack member 8 includes a pairof rack parts 47 and 48 and a connecting part 49 which connects both endportions of a pair of the rack parts 47 and 48. A pair of the rack parts47 and 48 is disposed in parallel to each other in a radial direction ofthe tooth-missing gear 46. In other words, the rack member 8 is aplate-like member which is provided with a pair of opposite parts whichface each other so as to interpose the tooth-missing gear 46therebetween and the connecting part 49 which connects both end portionsof the opposite parts. A pair of the opposite parts is provided with afirst rack part 47 that is formed in one of inner side portions extendedin parallel to each other in the opposite parts and a second rack part48 that is formed in the other of the inner side portions. An outputpart 85 protruding from an upper portion of the case body 15 is formedat an end portion on an opposite side to the portion where theconnecting part 49 is located in the first rack part 47.

Four tooth parts 471, 472, 473 and 474 are formed in the first rack part47. The thickness of the second tooth part 472 is formed thinner thanthose of other three tooth parts 471, 473 and 474. Three tooth parts481, 482 and 483 are formed in the second rack part 48. The thickness ofthe third tooth part 483 is formed thinner than those of other two toothparts 481 and 482.

As shown in FIG. 2(B), the tooth-missing gear 46 is formed with atooth-missing gear part 462 on an upper side in the axial direction of agear part 461, and a cam part 465 which is described below in detail isintegrally formed on its underside so as to overlap on the gear part461. In the tooth-missing gear 46, the tooth-missing gear part 462 isformed over an angular range of about 230 degrees in an outer peripheryof the tooth-missing gear 46, and a teeth part 463 comprised of threeteeth is formed at the center portion in a circumferential direction ofthe tooth-missing gear part 462 over an angular range of about 56degrees. Further, both side areas in the circumferential direction ofthe teeth part 463 of the tooth-missing gear part 462 are formed in thinplate parts 464 a, 464 b whose outer circumferential edge portion isformed in a circular arc shape. The thickness of the thin plate parts464 a, 464 b is set to be about half of the thickness of the teeth part463 and thus the thin plate parts 464 a, 464 b are capable ofoverlapping in the axial direction with the second thin tooth part 472of the rack part 47 and the third thin tooth part 483 of the rack part48. In this embodiment, as described below, the cam part 465 causescontact pieces to operate which structure switches for the small ACsynchronous motor 2.

(Structure of Control Circuit)

FIG. 4 is a circuit diagram showing a control circuit of a refrigeratoron which the opening/closing device shown in FIG. 1 is mounted. In FIG.4, in a control circuit 80 used in a real refrigerator, a compressor, athermostatic switch for on/off operation of the compressor, a fan motor,a switch for the fan motor and the like are required. However, thesestructures are omitted in FIG. 4 and only a motor drive circuit foropening or closing the baffle 7 is shown in the control circuit 80 of arefrigerator. Specifically, the control circuit 80 includes threeelements, i.e., a temperature sensor 83 which is serially-connected withan AC power supply 81, a switch part 84 which is comprised of a firstcontact piece 61, a second contact piece 62 and a third contact piece 63and is operated by the cam part 465 shown in FIGS. 3(A) and 3(C), andthe small AC synchronous motor 2.

In accordance with this embodiment, in order to structure the switchpart 84, as shown in FIGS. 3(A) and 3(C), the cam part 465 of thetooth-missing gear 46 is formed with two step parts 465 a, 465 b whichare recessed in the radial direction. Further, a first wirespring-shaped contact piece 61 is provided for falling in two step parts465 a, 465 b of the cam part 465, a second wire spring-shaped contactpiece 62 is provided for falling in only the step part 465 a, and athird wire spring-shaped contact piece 63 is provided for contactingwith and separating from the second contact piece 62. The first contactpiece 61 is formed to be the terminal “b” shown in FIG. 4, the secondcontact piece 62 is formed to be the terminal “c” shown in FIG. 4, andthe third contact piece 63 is formed to be the terminal “d” shown inFIG. 4. The cam part 465 is rotated with rotation of the tooth-missinggear 46 and three contact pieces 61, 62 and 63 are contacted with andseparated from with the rotation of the cam part 465 to change aconnecting state between the terminal “c” and the terminals “b” and “d”.In the following description, a switch formed with the first contactpiece 61 and the second contact piece 62 in the switch part 84 is set tobe an “A” switch and a switch formed with the third contact piece 63 andthe second contact piece 62 is set to be a “B” switch. In accordancewith this embodiment, in the control circuit 8, an end of a magnet wireof the small AC synchronous motor is connected to the terminal “c” andthe other end is connected to the terminal “a”.

The temperature sensor 83 is a thermostatic switch and, when atemperature in a chamber of a refrigerator becomes a predeterminedtemperature, e.g., 2° C. or lower, a terminal to be connected switchesto the terminal “b” from the terminal “d”. Further, when the temperatureof the chamber in the refrigerator becomes a predetermined temperature,e.g., 5° C. or higher, the terminal that is connected by the temperaturesensor 83 is switched to the terminal “d” from the terminal “b”.

(Operation)

An operation of the motor type damper device 1 in accordance with thisembodiment will be described with reference to FIGS. 3, 4 and 5. FIG. 5is a timing chart showing operations of a baffle and switches in theopening/closing device shown in FIG. 1.

First, the position of the baffle 7 shown by the solid line in FIG. 1 isset to be a fully closed stop position where the baffle 7 completelycloses the opening part 5. The positional relationship between the campart 465 and the respective contact pieces 61, 62 and 63 and thepositional relationship between the rack member 8 and the tooth-missinggear 46 in this state are shown in FIG. 3(A). In this case, thetooth-missing gear 46 is at the position of zero degree in the timingchart diagram shown in FIG. 5 and, in the control circuit 80 shown inFIG. 4, the “A” switch in the switch part 84 is turned on (the firstcontact piece 61 and the second contact piece 62 are in an “on” state)and the “B” switch is turned on (the third contact piece 63 and thesecond contact piece 62 are in an “on” state). Further, the temperaturesensor 83 is connected with the terminal “b”. In other words, this stateis a midway state where the baffle 7 is closing, for example, when thetemperature in the chamber becomes a predetermined temperature, e.g., 2°C. or lower, and the state just before the small AC synchronous motor 2is stopped.

Next, at the time point when the turning of the tooth-missing gear 46passes zero degree, the first contact piece 61 which has abutted withthe cam part 465 falls in the step part 465 b to be separated from thesecond contact piece 62. Therefore, the “A” switch of the controlcircuit 80 is turned off and the small AC synchronous motor 2 isstopped. On the other hand, since the third contact piece 63 ismaintained to be in contact with the second contact piece 62, the “B”switch is maintained in an “on” state.

As shown in FIG. 3(A), when the baffle 7 is in a fully closed state, thethin plate part 464 a of the tooth-missing gear 46 is engaged with thefirst tooth part 471 and the third tooth part 473 of the first rack part47 as a move preventing part and thus movement of the rack member 8 isprevented. In this case, the second tooth part 472 of the first rackpart 47 overlaps the thin plate part 464 a in the axial direction.

While the small AC synchronous motor 2 stops in the above-mentionedstate, the baffle 7 is continued in a closed state. Therefore, sincecold air is not introduced to the chamber of the refrigerator,temperature in the chamber rises. When temperature in the chamber risesa predetermined temperature, e.g., 5° C. or higher, the connection ofthe temperature sensor 83 is switched to the terminal “d” from theterminal “b”. In this case, since the “B” switch is in an “on” state,electric power is supplied to the small AC synchronous motor 2 again bythis switching to start driving.

When the small AC synchronous motor 2 starts to rotate in one direction,its rotation is transmitted to the gear part 461 of the tooth-missinggear 46 via a pinion 32, a first gear 42, a second gear 43, a third gear44 and a fourth gear 45. Therefore, the tooth-missing gear 46 turns inthe CCW direction (counterclockwise direction) shown by the arrow inFIG. 3(A) and thus the cam part 465 also turns in the CCW direction(counterclockwise direction) shown by the arrow.

Then, as shown in FIG. 3(B), when the tooth part 463 of thetooth-missing gear part 462 of the tooth-missing gear 46 begins toengage with the first rack part 47, the rack member 8 is linearly drivenin a direction shown by the arrow “T1” in FIG. 3(B) and the baffle 7begins to turn in an open direction.

When the rack member 8 is linearly driven in the direction shown by thearrow “T1” as described above, the second rack part 48 does not engagewith any portion of the tooth-missing gear part 462. In other words, thesecond rack part 48 engages with neither of the tooth part 463 and thethin plate parts 464 a and 464 b. Therefore, the movement of the rackmember 8 is permitted and the rack member 8 is smoothly and linearlydriven in the “T1” direction.

When turning of the tooth-missing gear 46 continues and thetooth-missing gear 46 is turned by 180 degrees, as shown in FIG. 3(C),the tooth-missing gear part 462 is completely separated from both thefirst rack part 47 and the second rack part 48. At this point, thebaffle 7 turns by 45 degrees from the fully closed state and moves to afull open position shown by the dotted line in FIG. 1. When the baffle 7is in the fully opened state, the thin plate part 464 a of thetooth-missing gear 46 engages with the second tooth part 482 of thesecond rack part 48 and the inner peripheral face of the connecting part49 to prevent the movement of the rack member 8. In this case, the thirdtooth part 483 of the second rack part 48 overlaps the thin plate part464 a in the axial direction.

At the time point when the turning of the tooth-missing gear 46 passesthrough the point of 180 degrees, the second contact piece 62 which hasabutted with the cam part 465 falls in the step part 465 a to beseparated from the third contact piece 63. Therefore, since the “B”switch of the control circuit 80 is turned off, the small AC synchronousmotor 2 stops. In this case, the first contact piece 61 comes intocontact with the second contact piece 62 to be turned in an ON state andthus the “A” switch is turned in an ON state.

While the small AC synchronous motor 2 has stopped in theabove-mentioned state, the baffle 7 is maintained in the open state.Therefore, temperature in the chamber is dropped by introduction of coldair to the chamber of the refrigerator.

After that, when the temperature in the chamber falls to a predeterminedtemperature, e.g., 2° C. or lower, the terminal which is connected bythe temperature sensor 83 is switched to the terminal “b” from theterminal “d”. At this time point, since the “A” switch is in an ONstate, electric power is supplied to the small AC synchronous motor 2again to start driving in accordance with this switching.

When the small AC synchronous motor 2 starts to rotate in one directionagain, the tooth-missing gear 46 starts to turn again in the CCWdirection shown by the arrow. FIG. 3(D) shows the state where thetooth-missing gear 46 is turned by 191 degrees and, at the time pointwhen the turning has passed 191 degrees, the “B” switch of the switchpart 84 is turned on (the second contact piece 62 and the third contactpiece 63 are turned to be ON). When its turning angle becomes 226degrees, as shown in FIG. 3(E), the teeth part 463 of the tooth-missinggear part 462 begins to engage with the second rack part 48. When thetooth-missing gear part 462 and the second rack part 48 are engaged witheach other, the rack member 8 is begun to be linearly driven in adirection shown by the arrow “T2” in FIG. 3(E) and the baffle 7 beginsto turn in the close direction.

While the second rack part 48 is linearly driven in the direction shownby the arrow “T2”, the first rack part 47 does not engage with anyportion of the tooth-missing gear part 462. In other words, the firstrack part 47 does not engage with the teeth part 463 and the thin plateparts 464 a and 464 b. Therefore, movement of the rack member 8 ispermitted and the rack member 8 is smoothly and linearly moved in the T2direction.

When the turning angle of the tooth-missing gear 46 becomes 320 degrees,the baffle 7 becomes in a fully closed state. Further, the “A” switch ofthe control circuit 80 is continued to be in an “ON” state and both the“A” switch and the “B” switch are continued to be in an “ON” state.

When the tooth-missing gear 46 turns once (360 degrees), the “A” switchis turned to be off and rotation of the small AC synchronous motor 2stops. As a result, the baffle 7 continues to be in a fully closed stateuntil temperature in the chamber rises to 5° C. or higher.

The chamber of a refrigerator is maintained in a specified temperaturerange by repeating the above-mentioned operation.

PRINCIPAL EFFECTS OF THIS EMBODIMENT

As described above, in the driving force transmission mechanism 3 in themotor type damper device 1 in accordance with this embodiment, when thesmall AC synchronous motor 2 rotates in one direction and thetooth-missing gear part 462 of the tooth-missing gear 46 engages withthe first rack part 47 of the rack member 8, the rack member 8 is movedupward and the baffle 7 is operated in the open direction and, when thetooth-missing gear part 462 engages with the second rack part 48 of therack member 8, the rack member 8 is moved downward and the baffle 7 isoperated in the close direction. As described above, even when thebaffle 7 is operated in both directions, the tooth-missing gear 46 isonly required to be turned in a counterclockwise direction as shown bythe arrow “CCW” and rotation of the small AC synchronous motor 2 is notrequired to be reversed, and thus the structure of the control circuit80 for the motor type damper device 1 can be simplified.

Further, the rack member 8 is a plate-like member which is provided witha pair of the opposite parts that face each other across thetooth-missing gear 46 and the connecting part 49 that connects the endportions of the opposite parts. Further, the first rack part 47 and thesecond rack part 48 are respectively formed on a pair of the inner sideportions which are extended in a parallel manner in the opposite parts.In other words, the rack parts 47 and 48 are disposed in parallel eachother in the radial direction of the tooth-missing gear 46. The rackpart 47 engages with the teeth part 463 on one side in the radialdirection of the tooth-missing gear 46 and the rack part 48 engages withthe teeth part 463 on the other side in the radial direction. Therefore,the rack member 8 can be driven in both directions only with thetooth-missing gear 46 and thus reduction of number of components andspace saving can be attained. Further, since the first rack part 47 andthe second rack part 48 are extended so as to be parallel to each other,the rack member 8 can be reciprocated only in the extending direction ofthe first rack part 47 and the second rack part 48. Therefore, sinceoperating space of the rack member 8 may be narrowed, the size of themotor type damper device 1 can be reduced.

Further, when the teeth part 463 engages with the first rack part 47 todrive the rack member 8, the teeth part 463 does not engage with thesecond rack part 48. Therefore, the rack member 8 does not receiveunnecessary force between the second rack part 48 and the tooth-missinggear part 462. Similarly, when the teeth part 463 engages with thesecond rack part 48 to drive the rack member 8, the teeth part 463 doesnot engage with the first rack part 47. Therefore, the rack member 8does not receive unnecessary force between the first rack part 47 andthe tooth-missing gear part 462. Accordingly, the rack member 8 can beefficiently and smoothly driven.

Other Embodiments

The present invention has been described in detail using theembodiments, but the present invention is not limited to the embodimentsdescribed above and many modifications can be made without departingfrom the present invention.

For example, in the embodiment described above, the U-shaped rack member8 is used in which two rack parts 47 and 48 are disposed in parallel toeach other in the radial direction of the tooth-missing gear 46.However, for example, as shown in FIG. 6, a straight-shaped rack member8′ may be used in which two rack parts 47′ and 48′ are formed inportions on each other's back face side.

In other words, a driving force transmission mechanism is provided as agear with a first tooth-missing gear 46 a on one side of both sides ofthe rack member 8′ and a second tooth-missing gear 46 b on the otherside. Teeth parts 461 a and 461 b of two tooth-missing gears 46 a and 46b engage with an intermediate gear 45′ and rotation of a motor (notshown) is transmitted to the teeth parts 461 a and 461 b through theintermediate gear 45′. Further, in the driving force transmissionmechanism, the rack member 8′ is provided with a pair of outer sideportions which face opposite directions and are extended in parallel toeach other. The first rack part 47′ is formed in one of a pair of theouter side portions and the second rack part 48′ is formed in the otherof a pair of the outer side portions. The first rack part 47′ is capableof engaging with the teeth part 463 a of the first tooth-missing gear 46a and the second rack part 48′ is capable of engaging with the teethpart 463 b of the second tooth-missing gear 46 b. Further, the rackmembers 47′ and 48′ are formed at positions that are shifted in thedriving direction of the rack member 8′ (longitudinal direction of therack member 8′).

Therefore, when the motor rotates in one direction and the intermediategear 45′ rotates in a direction shown by the arrow “CW”, both twotooth-missing gears 46 a and 46 b are turned in a direction shown by thearrow “CCW” and, when the first rack part 47′ and the teeth part 463 aof the first tooth-missing gear 46 a are engaged with each other, therack member 8′ is driven in a “T2” direction. In this case, the secondrack part 48′ is in a non-engagement state with the teeth part 463 b ofthe second tooth-missing gear 46 b. Next, when the motor further rotatesin one direction and the intermediate gear 45′ rotates in the directionshown by the arrow “CW”, both two tooth-missing gears 46 a and 46 b areturned in the direction shown by the arrow “CCW” and, when the secondrack part 48′ and the teeth part 463 b of the second tooth-missing gear46 b are engaged with each other, the rack member 8′ is driven in a “T1”direction. In this case, the first rack part 47′ is in a non-engagementstate with the teeth part 463 a of the first tooth-missing gear 46 a.

Further, in the rack member 8 of the driving force transmissionmechanism 3 in accordance with the embodiment described with referenceto FIG. 1 through FIG. 5, the connecting part 49 is located on one endportion and the output part 85 is protruded from the other end portionof the rack member 8′. However, as shown in a driving force transmissionmechanism 3′ in FIG. 7, an output part 85′ may be structured so as to beprotruded from an end portion of the rack member 8′ on the side where aconnecting part 49′ is located.

Further, in the embodiment described above, the small AC synchronousmotor 2 which rotates in one direction is used as a motor. However,other motors which rotate in one direction or motors capable of rotatingin both directions such as a DC motor and a stepping motor may beutilized. Further, the turning direction of the tooth-missing gear 46 isnot limited to the “CCW” direction and the tooth-missing gear 46 may beturned in the “CW” direction.

In addition, in the embodiment described above, the open position of thebaffle 7 is structured so as to be substantially parallel to the frame4. However, the present invention is not limited to this embodiment andthe open position of the baffle 7 may be set in an inclined position.

In addition, in the embodiment described above, the frame 4 of the motortype damper device 1 is formed in a duct shape. However, the presentinvention may be applied to other types of a damper device. Further,except a refrigerator, the present invention may be applied to variousopening/closing devices for controlling other fluid such as a duct forventilation and a drain valve for a washing machine.

Further, the present invention may be applied to an opening/closingdevice except a damper device, for example, other motor typeopening/closing devices such as a motor type opening/closing device fordriving a louver of an air-conditioner.

INDUSTRIAL APPLICABILITY

In a motor actuator in accordance with the present invention, a gear inthe driving force transmission mechanism rotates in one direction and,when the tooth-missing gear part engages with a first rack part of arack member, the rack member is moved in one direction and, when thetooth-missing gear part engages with the second rack part of the rackmember, the rack member is moved in the other direction. As describedabove, even when a driven member is operated in both directions, it isonly required that the gear is rotated in one direction and rotation ofa motor is not required to be reversed, and thus the control circuit forthe motor actuator can be simplified.

While the preferred embodiments of the present invention have beendescribed using specific terms, such description is for illustrativepurposes only, and it is to be understood that changes and variationsmay be made without departing from the spirit or scope of the appendedclaims. The presently disclosed embodiments are therefore to beconsidered in all respects as illustrative and not restrictive, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

1. A motor actuator in which a driving force of a motor is transmittedto a driven member through a driving force transmission mechanism tooperate the driven member, wherein, the driving force transmissionmechanism comprises a gear which is rotationally driven by the motor anda rack member which is linearly driven by the gear to operate the drivenmember, and the gear is provided with a tooth-missing gear part in whicha teeth part is formed at a predetermined position in a circumferentialdirection of the gear, and the rack member is provided with a first rackpart which causes the rack member to move in one direction when themotor rotates in one direction and the first rack part engages with thetooth-missing gear part and a second rack part which causes the rackmember to move in the other direction when the motor rotates in the onedirection and the second rack part engages with the tooth-missing gearpart.
 2. The motor actuator according to claim 1, wherein thetooth-missing gear part is in a non-engagement state with the secondrack part when the tooth-missing gear part engages with the first rackpart and the tooth-missing gear part is in a non-engagement state withthe first rack part when the tooth-missing gear part engages with thesecond rack part.
 3. The motor actuator according to claim 1, whereinthe first rack part and the second rack part are extended in parallel toeach other.
 4. The motor actuator according to claim 1, wherein the rackmember is provided with a pair of inner side portions between which thegear is disposed and which are extended in parallel to each other, andthe first rack part is formed in one of a pair of the inner sideportions and the second rack part is formed in the other of a pair ofthe inner side portions.
 5. The motor actuator according to claim 1,wherein the driving force transmission mechanism includes, as the gear,a first gear on one side of both side positions of the rack member and asecond gear on the other side of the both side positions, and the rackmember is provided with a pair of outer side portions which face inopposite directions and are extended in parallel to each other, and thefirst rack part is formed in one of a pair of the outer side portionsand the second rack part is formed in the other of a pair of the outerside portions.
 6. An opening/closing device provided with the motoractuator recited in claim 1, wherein the driven member is anopening/closing member whose position is changed between an openposition and a close position by the rack member.